1. Technical Field of the Invention
This invention relates generally to communication networks, and more particularly, to a method and apparatus for decreasing the jitter and average delay experienced by voice packet streams while also conserving bandwidth in a packetized network.
2. Description of the Related Art
In Voice over Packet (VoP) network systems, the end to end network delay and the variation in the time between packets arriving, caused by network congestion, timing drift, or route changes (also known as jitter variation) are important quantities to consider when providing an acceptable level of Quality of Service (QoS) for the delay sensitive voice traffic flow.
FIG. 1 is a block diagram conceptually illustrating the sources of delay and jitter in a VoP network. FIG. 1 shows an originating gateway 2, a VoP network 4, and a destination gateway 6.
A gateway is a network point that acts as an entrance to another network. On the Internet, a node or stopping point can be either a gateway node or a host (end-point) node. Both the computers of Internet users and the computers that serve pages to users are host nodes. The computers that control traffic within a company's network or at a local Internet service provider (ISP) are gateway nodes. A gateway is often associated with both a router, which knows where to direct a given packet of data that arrives at the gateway, and a switch, which furnishes the actual path in and out of the gateway for a given packet. The above definitions are basic and well-known to network engineers.
In the diagram of FIG. 1, the sources of delay and jitter variation are threefold. First, on the originating gateway 2, delay and jitter is contributed by voice and DSP processing. Secondly, delay and jitter are contributed by elements of the voice gateway 2 that multiplex the voice packets. Thirdly, additional delay and jitter is contributed by all the network elements in the VoP network 4 between the originating voice gateway 2 and the destination voice gateway 6.
Many carriers use Voice over ATM Adaptive Layer 2 (VoAAL2) trunks for supporting their wireless networks. A typical scenario involves ATM trunks being established between the Mobile Switching Centers (MSCs) in order to carry the voice traffic collected by wireless Base Switching Centers (BSCs). These trunks offer a means to transport huge quantities of voice data with good bandwidth savings.
However, many times these trunks go through some ATM clouds (included in the VoP network 4) that are under a different carrier's control. In this situation, where there are multi-carrier segments in the VoP network 4, one carrier loses the ability to have total control of the delay and jitter performance because the third source of delay and jitter described above is no longer attributable to the one carrier.
Embodiments of the invention address this and other disadvantages of the conventional art.